feat: Add OpenAI-compatible provider nodes

- Support multiple OpenAI-compatible providers with custom prefix/baseUrl
- Add provider nodes CRUD (create/read/update/delete)
- URL building: baseUrl + /chat/completions or /responses
- Model import from /models endpoint
- API key validation via /models
- Usage type safety across all translators
- OAuth token auto-refresh for expired tokens

src/shared/constants/models.js

@@ -10,7 +10,7 @@ export {
   getModelsByProviderId
 } from "open-sse/config/providerModels.js";
 
-import { AI_PROVIDERS } from "./providers.js";
+import { AI_PROVIDERS, isOpenAICompatibleProvider } from "./providers.js";
 import { PROVIDER_MODELS as MODELS } from "open-sse/config/providerModels.js";
 
 // Providers that accept any model (passthrough)
@@ -22,6 +22,7 @@ const PASSTHROUGH_PROVIDERS = new Set(
 
 // Wrap isValidModel with passthrough providers
 export function isValidModel(aliasOrId, modelId) {
+  if (isOpenAICompatibleProvider(aliasOrId)) return true;
   if (PASSTHROUGH_PROVIDERS.has(aliasOrId)) return true;
   const models = MODELS[aliasOrId];
   if (!models) return false;